Bottle trees originated in the Congo. Slaves who came to America hung up these glass bottles because they believed that they captured spirits. The bottle trees make a strange hollow noise when the wind blows through them. The people who made them believed that these were the spirits yelling to get out.
Bottle trees became garden staples for folk artists in the American south. In Europe, the bottle trees evolved into "witch balls" which are also known as gazing globes. They don't make any noise. Today, you can see bottle trees in many gardens as the tradition lives on for aesthetic purposes.
Here's a collection of beautiful bottle trees:
You can learn more about bottle trees and how to make one here.